This new tutorial DevShed has posted today talks about planning for your application's security and some handy tips you can use to keep it safe.

In this article we will look at how to start a project while considering its related security issues. We will focus on form validation as well as other topics such as site structures. To demonstrate the topics that we will be discussing, we will create a site that will enable a user to log in, log out, register and manage passwords.

They look at things like the overall structure of the site (including how it lives on the file system) and protecting your application from dangerous user input through forms.